The New York Times reports that the Mars Rover Spirit may have inadvertently discovered evidence of an environment on Mars that may have supported life:
SAN FRANCISCO — The lame wheel on the NASA Mars rover Spirit has proved an invaluable science tool, turning up evidence of a once habitable environment, scientists said Monday.
The right front wheel of Spirit stopped turning in March 2006. Since then, the rover has been driving backwards, dragging the lame wheel along. This May, scientists noticed a bright spot in the trail of overturned dirt.
They turned Spirit around for a closer look, finding high levels of silica, the main ingredient of window glass. They then aimed the rover at a nearby rock, wanting to break it apart to determine if the silica was just a surface coating, or if the rock was silica all the way through.
The target rock survived Spirit’s charge, but a neighboring rock cracked open. The interior of that rock, which the scientists informally named “Innocent Bystander,” turned out to be rich in silica.
On Earth, such high concentrations of silica can form in only two places: a hot spring, where the silica is dissolved away and deposited elsewhere, or a fumarole, an environment, often near a volcano, where acidic steam rises through cracks. The acids dissolve other minerals, leaving mostly silica. On Earth, both environments teem with life.
Whether that was the case on Mars in the past, or may even be the case today, remains to be seen.